Innumerable occasions arise in many industrial applications in which it is found desirable to connect one chain to another or to shorten the length of a chain. In such circumstances, any one of a variety of devices may be used. For example, any of the chain grab or claw hooks such as those disclosed in U.S. Pat. Nos. 3,741,599; 3,601,978; 1,470,481; 3,673,646; 2,978,767; 3,333,412, or 3,233,933 may be attached to the end of a chain by a conventional shackle and load pin. The procedure of attaching a single hook to one end of a chain, however, involves considerable time and inconvenience. Subsequent removal of the attached hook, while seemingly of a trivial nature, may become very difficult to execute if the load pin has been bent or otherwise distorted while loaded, so that considerable additional time and effort may be extended in extracting the load pin.
Efforts to cure the above described difficulties in the use of a load pin-shackle-grab or claw hook for chain shortening or chain-to-chain connection have led to the development of a large number of chain-to-chain connecting devices exemplified by U.S. Pat. Nos. 3,747,971; 3,027,615; 3,041,041; 3,511,527; 1,224,148; 1,531,770; 1,758,744; 1,314,747; and 3,729,926, as well as the well known coupler or shortening device which consists of a pair of eye type chain grab hooks connected by a short length of interconnecting chain. Each of the devices disclosed in the patents listed above, however, have the shortcoming that they are specially adapted for the singular purpose of chain shortening or chain-to-chain connecting. They are not adapted for permanent or removable attachment to the end of a chain as a load bearing device. Accordingly, a workman must have on hand not only the chain coupling and shortening devices but also one or more conventional hooks which may be attached to the end of a chain as previously described.